Wnt/beta-catenin signal transduction pathway is involved in corpus luteum development and luteal function in gonadotropin-treated rats

PAULA ACCIALINI

Woods Hole

Simposio; 19th Annual FIR Symposium; 2016

The evolutionarily conserved Wnt/β-catenin signal transduction pathway controls many biological processes. The objective of this study was to determine the role of this signaling pathway in follicular development and luteal function. To this purpose eCG gonadotropin- prepubertal treated female rats were injected with a Wnt inhibitor (XAV939, 5ug/ovary, Wnt-I group) or vehicle (DMSO, Control group) into the bursa of both ovaries the day of hCG administration. Two days after hCG and Wnt inhibitor or vehicle injection, blood samples and ovaries were collected. Corpora lutea (CL) from one ovary were isolated by microdissection and resuspended in lysis buffer for protein extraction. The other ovary was fixed in Bouin solution for histological analysis and immunohistochemistry (IHC). Ovarian function was evaluated by measuring serum progesterone (P4) (RIA), protein levels by western blot and ovarian structures at different stages of development by Hematoxylin-eosin staining 48 hours after XAV939 treatment. The percentage of each ovarian follicle structures analyzed was not different between the treated and control groups. However, the percentage of CL showed a significant decrease in ovaries injected with XAV939 in comparison with the control group. Interestingly, the treatment with the β-catenin inhibitor generated cystic structures. The levels of P4 significantly decreased after Wnt inhibitor administration. CL protein levels of StAR significantly decreased in the Wnt-I group in comparison with the Control group, whereas the levels of P450scc or 3βHSD enzymes did not change. PCNA protein levels significantly decreased in the Wnt-I group in comparison with the Control group. IHC studies showed PCNA staining in small cells from the CL, corresponding to small luteal cells or other CL components such as endothelial cells. Wnt inhibition also produced an increase in proapoptotic and a decrease in antiapoptotic proteins levels. Studies of angiogenic markers showed a significant decrease in the endothelial marker Lectin BS-1 staining in the Wnt-I group and a significant decrease in VEGF120 isoform protein levels. In conclusion, the inhibition of Wnt pathway produces a decrease in CL and the presence of cystic structures. A decrease in P4 serum levels apparently associated to a decrease in StAR levels in CL, an imbalance between antiapoptotic:proapoptotic proteins and a decrease in CL´s cells proliferation.